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-   -   Welcome to my $#@! ECM... (http://www.wranglerforum.com/f218/welcome-to-my-ecm-139318.html)

Random_Walk 02-12-2012 10:01 PM

Welcome to my $#@! ECM...
 
Okay - got the beast all wired up, but found one bit that's not quite right, and it's driving me nuts...

Everything is accounted for and works fine, except for one circuit. Unfortunately, it's the one that closes the fuel pump and auto shutoff relays.

The circuit leaves pin 50-something (I can look it up), which is the Fuel Pump Relay pin. It feeds the coils on the two aforementioned relays, goes through them, then comes back to pin 9 (Ignition Sense Circuit). The problem is that I only get 2.36V on that circuit when checking to ground. Is that correct? I was thinking that perhaps it should be 12 volts (given the relays), but I need to know for certain... I'm not certain if the voltage is sufficient to pull the relays, and I have tested the fuel pump and injectors, the coil, and everything else that those relays feed (they work). It's just that one circuit that keeps failing to pull the relays (I tested the two relays on the starter socket... they work too).

I really don't want to have to fork out for a new ECM, but it may appear to be what's coming... when I pulled the old fuse block, it was half-melted, so I was worried the the ECM was half dead anyway.

For those who recommend replacing the ECM, I need a favor - know of any good stores that can program/sell them, and ship them within less than a month (my lease is expiring, and I'm sure the landlord wants it gone by then...)

olbaid_83 02-12-2012 10:11 PM

its a long shot but check the wire you are using. make sure its not shorting somewhere. i may be waaaay of with this idea but if the wire is bad in any way shape or form you will get bad voltage readings throughout. please someone correct me if im wrong though. it just seems on that everything else tests good. i had bad ecm's in a bike and when they go, lots of things stop working right. not just one thing. similar problem with a cbr i had. kept running richer and richer till it would foul out plugs in a matter of seconds. after losing my mind and preparing to buy a new ecm, found out it was a bad tps. also if you know anyone who has a known good ecm you could swap out and test. hope it helps. gl

Random_Walk 02-13-2012 05:24 PM

I did follow it back and forth (it's a pair of relatively short wires, as the circuit hikes over from the ECM to the relays, then back to the ECM.)

I'll probably have to break down and get a new/used ECM. I might be able to hit a local junkyard and scare one up that way.

Not 100% sure swapping them out is the smartest thing, though, especially since you have to program in the VIN, mileage, and little details like that. I know if the engine and ECM aren't matched (e.g. can't use one out of a 4-banger), things will go splat in a hurry.

olbaid_83 02-13-2012 08:16 PM

Wasn't aware of that. That's how we tested ecms in bikes all the time. Obviously you couldn't put one from a 4 banger in a 6 but I figured the same model and trim would be ok

STUUPID 02-14-2012 05:14 PM

Yayyy.....my favorite subject....not really, I have been dealing with the same issue for three months after building a nice 4.0....the circuit you are checking is the asd relay circuit. Supplies voltage to cps, cam sensor, o2 sensor, fuel injectors, also from alternator field circuit, tps and probably more than I can remember. The computer supplies the ground to the relay to energize it and it in turn supplies voltage to all the above...if I ever meet the ass that designed this I will kick him in his balls! A bad ground can cause this, a grounded sensor wire can also cause this, usually it kills the ecm. I had ecm rebuilt at autozone and repaired damaged wires...still has issue....tried another ecm...still has issue. In the middle of replacing harness, even after I have traced all wires and ohm tested...voltage tested etc. has me baffled. If the harness does not work, next I will purchase a stand alone and throw the original stuff inn the fire.


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